Dry disconnect couplings are used in various applications to connect one fluid conduit to another to form a continuous flow path. For example, dry disconnect couplings are used to form a continuous flow path between a storage tank and a tanker truck for transferring petroleum products and chemicals, such as fuel, at a storage tank farm. Typically, the dry disconnect coupling includes an adapter and a coupler. The adapter is attached to the fill pipe of a tanker truck at one end and to the coupler at the other end. The coupler is attached at its free end to a transfer hose from the storage tank. The adapter and the coupler each define a flow passageway therethrough which is sealed by a poppet valve. The poppets may be opened simultaneously by displacing the poppet of the coupler in the direction of the adapter to complete the continuous flow path.
As the fuel is transferred from the storage tank to the tanker truck, a small amount of fuel accumulates on the end faces of the poppets. After the transfer operation is completed and the coupling is uncoupled, the fuel residue on the end faces of the poppets may be spilled onto the ground in the vicinity of the coupling. Although the amount of fuel that may be spilled after each transfer operation is generally less than an ounce, repeated transfer operations can result in significant contamination of the ground. Accordingly, it is desirable to provide a dry disconnect coupling for connecting a transfer hose from a storage tank to the fill pipe of a tanker truck which includes means for returning fuel residue that accumulates on the end faces of the adapter and the coupler to the flow path or to an external reservoir.
A dry disconnect coupling is disclosed in U.S. Pat. No. 5,273,071 issued Dec. 23, 1993 to Oberrecht. The Oberrecht coupling consists of an adapter connected to a liquid conduit at one end and to a coupler at the other end. The coupler is in turn connected to another liquid conduit. The adapter and the coupler each define a flow passageway and include a poppet valve. When closed, the poppets seal the adapter and the coupler. When opened, the poppets permit liquid to flow between the conduits through the flow passageways.
The coupler of the Oberrecht coupling is provided with an O-ring mounted in a groove formed in the end face of the poppet. When the poppets are opened, the O-ring seals the end faces of the poppets to prevent the end faces from being wetted with fuel during transfer operations. The O-ring thus minimizes the amount of fuel residue that accumulates on the end faces of the poppets which could be a source of contamination when the coupling is disconnected.
Fuel residue may, however, accumulate around the periphery of the seal. The fuel residue is not returned to the flow path or to an external reservoir, but instead may travel around the periphery of the seal under the influence of gravity and collect at the bottom of the seal opposite the ground. Thus, when the coupling is uncoupled the fuel residue may spill and contaminate the ground in the vicinity of the coupling. Further, the O-ring may become worn. If not replaced, the worn O-ring may leak and permit fuel to collect on the end faces of the coupler and the adapter. Thus, the fuel residue likewise may spill when the coupling is disconnected and contaminate the surrounding ground.